1. Field of the Invention
The present invention relates to a reference voltage generation circuit.
2. Description of the Related Art
Electronic devices to be worn on person, typically, wearable devices, are each small in size, and the capacity of a battery installed in the devices accordingly tends to be small. Since the electronic devices to be worn on person have the battery of which the capacity is small in many cases, an electronic circuit to be installed in the electronic devices to be worn on person is demanded to be small in size and low in current consumption.
A way to run an electronic circuit to be installed in the electronic devices to be worn on person on low current consumption is to save power by putting the electronic circuit in a normal operation state only when the electronic circuit is in use, and putting the electronic circuit in a non-operation state while not in use. For further power saving, the normal operation state and the non-operation state may be switched quickly when the electronic circuit is in use as well. That is, the electronic circuit may intermittently operate, thereby saving the power in the normal operation state.
Further, it is common to add a stabilizing capacitor to a reference voltage generation circuit in an electronic circuit running on low current consumption, in order to stabilize output against anticipated disturbance from external noise.
However, the stabilizing capacitor is charged with a small amount of current if a reference voltage generation circuit running intermittently shifts from the non-operation state to the normal operation state, and the output of the reference voltage generation circuit consequently takes time to reach stability. In consideration of this circumstance, a circuit for rapidly charging the stabilizing capacitor is being investigated.
FIG. 7 illustrates a reference voltage generation circuit 1 of the related art (Japanese Patent Application Laid-open No. 2004-280805). The reference voltage generation circuit 1 includes a reference voltage circuit 2, a stabilizing capacitor 3, a rapid reference voltage stabilizer 4, a shut-down circuit 5, a sub-reference voltage circuit 6, and a comparator 7. The reference voltage generation circuit 1 has a function of rapidly charging the stabilizing capacitor in a shift from the non-operation state to the normal operation state and of automatically stopping the rapid charge operation when a stable voltage is reached.
However, a drawback is that a conventional reference voltage generation circuit such as the reference voltage generation circuit 1 requires a comparator for comparison between the reference voltage circuit and the sub-reference voltage circuit. A high-speed operation comparator is required in order to accomplish quick activation of the reference voltage generation circuit, and thereby invites an increase in the circuit scale of the comparator and an increase in current consumption.